Next story in Science

This track is an example of simulated data modeled for the CMS detector on the Large Hadron Collider (LHC) at CERN. Here a Higgs boson is produced and then decays into two jets of hadrons and two electrons. The lines represent the possible paths of particles produced by the proton-proton collision in the detector while the energy these particles deposit is shown in blue.

A rumor is floating around the physics community that the world's largest atom smasher may have detected a long-sought subatomic particle called the Higgs boson, also known as the "God particle."

The controversial rumor is based on what appears to be a leaked internal note from physicists at the Large Hadron Collider (LHC), a 17-mile-long particle accelerator near Geneva, Switzerland. It's not entirely clear at this point if the memo is authentic, or what the data it refers to might mean — but the note already has researchers talking.

The buzz started when an anonymous commenter recently posted an abstract of the note on Columbia University mathematician Peter Woit's blog, Not Even Wrong.

Some physicists say the note may be a hoax, while others believe the "detection" is likely a statistical anomaly that will disappear upon further study. But the find would be a huge particle-physics breakthrough, if it holds up.

"If it were to be real, it would be really exciting," said physicist Sheldon Stone of Syracuse University.

Hunting for the Higgs
The Higgs boson is predicted to exist by prevailing particle-physics theory, which is known as the Standard Model. Physicists think the Higgs bestows mass on all the other particles — but they have yet to confirm its existence.

Huge atom smashers — like the LHC and the Tevatron, at Fermilab in Illinois — are searching for the Higgs and other subatomic bits of matter. These accelerators slam particles together at enormous speeds, generating a shower of other particles that could include the Higgs or other elemental pieces predicted by theory but yet to be detected.

The leaked note suggests that the LHC's ATLAS particle-detection experiment may have picked up a signature of the elusive Higgs. The signal is consistent, in mass and other characteristics, with what the Higgs is expected to produce, according to the note.

However, some other aspects of the signal don't match predictions.

"Its production rate is much higher than that expected for the Higgs boson in the Standard Model," Stone told Space.com in an email interview. So the signal may be evidence of some other particle, Stone added, "which in some sense would be even more interesting, or it could be the result of new physics beyond the Standard Model."

Too soon to tell
Stone was quick to point out that the note is not an official result of the ATLAS research team. Therefore, speculating about its validity or implications is decidedly preliminary.

"It is actually quite illegitimate and unscientific to talk publicly about internal collaboration material before it is approved," Stone said. "So this 'result' is not a result until the collaboration officially releases it."

Other researchers joined Stone in urging patience and caution before getting too excited about the possible discovery.

While it's still early, some researchers have already begun to cast doubt on the possible detection. For example, Tommaso Dorigo — a particle physicist at Fermilab and CERN, which operates the LHC — thinks the signal is false and will fade upon closer inspection.

Dorigo — who said he doesn't have access to the full ATLAS memo — gives several reasons for this viewpoint. He points out, for example, that scientists at Fermilab didn't see the putative Higgs signal in their Tevatron data, which covered similar ground as the ATLAS experiment.

Dorigo feels strongly enough, in fact, to put his money where his mouth is.

"I bet $1,000 with whomever has a name and a reputation in particle physics (this is a necessary specification, because I need to be sure that the person taking the bet will honor it) that the signal is not due to Higgs boson decays," he wrote on his blog today. "I am willing to bet that this is NO NEW PARTICLE. Clear enough?"

The Standard Model of particle physics is one of science's most successful theories, enabling the development of devices ranging from light bulbs, to microwave ovens and television, to quantum computing devices. The Standard Model is also one of the oddest theories, because it lays out a dizzying menagerie of hundreds of subatomic particles. At its heart are 16 types of elementary particles ... plus at least one more mysterious particle that scientists are spending billions of dollars to detect.

Click on "Next" to get the full rundown.

Quarks

Berkeley Lab

Six "flavors" of quarks have been detected: up and down, charm and strange, top and bottom. Quarks are almost always found in different combinations, bound together by gluons (more on those later). Particles built up from quarks and gluons are called hadrons. The Large Hadron Collider is so named because it's a large collider that smashes hadrons together.

Three-quark combinations fit in the category of baryons. The best-known baryons are the proton (with two up quarks and one down quark) and the neutron (with two down quarks and one up quark).

Particles that have one quark and one antiquark fit in the category of mesons. For example, the pion, or pi meson, contains an up quark and an anti-down quark.

Six "flavors" of leptons have been detected: The negatively charged electron is the best-known lepton — along with its antimatter counterpart, the positron. This photo shows the path of single electrons passing through liquid helium, in an experiment devised by Brown University researchers.

The muon is also negatively charged, but it's about 207 times as massive as the electron. ("Who ordered that?" physicist Isidor Rabi reportedly asked.) The negatively charged tau particle is even bigger — 3,477 times as massive as the electron — but it decays into other particles in less than a trillionth of a second.

Each of those leptons has a neutrino associated with it: the electron neutrino, the muon neutrino and the tau neutrino. Neutrinos interact only weakly with other particles, and they zip through our planet virtually without a trace. Physicists only recently determined that they have mass, but there's still a great deal of mystery surrounding the ghostly particles.

Force carriers

Fermilab

The Standard Model sets aside a category for particles that are associated with force fields. The effect of a field can be viewed as involving an exchange of such force-carrying particles.

Four elementary force-carrying particles have been detected. The best-known force carrier is the photon — which plays a part in the electromagnetic spectrum, including visible light. The gluon binds quarks together through the strong nuclear force. The weak nuclear force involves the exchange of W and Z bosons. The W boson can carry a positive or a negative charge, while the Z boson is neutral.

If gravity could be incorporated into the Standard Model, the force-carrying particle would be called the graviton (shown here in an artist's depiction). However, gravitons have not yet been detected, and at least for now, such particles are not accounted for in the Standard Model.

Bosons vs. fermions

Rice Univ. via AIP

All force-carrying particles are bosons, but not all bosons are force carriers. The difference has to do with a property known as particle spin. Particles with a fractional spin value (for example, electrons, protons and neutrons) are fermions. Two identical fermions cannot occupy the same quantum state. This is a property that keeps electrons from collapsing into a jumble, and thus makes chemical reactions possible.

All particles with a whole-integer spin value are classified as bosons, and such particles can occupy the same quantum state even if they're identical. The photon is the best-known type of boson.

Even atoms can be classified as fermions and bosons. This photo shows how atom clouds of lithium-7 (bosons) and lithium-6 (fermions) behave at low temperatures. The bosons collapse into a compact cloud, while the fermions can't squeeze that closely together.

The Higgs boson is the only particle predicted by the Standard Model that has not yet been detected. The Higgs is the main quarry for physicists at the Large Hadron Collider. This image is a simulation of the Higgs' signature as it might appear in one of the LHC's detectors.

The Higgs boson, named after Scottish theorist Peter Higgs, is thought to be associated with a field that endows some particles (such as the weak nuclear force's W and Z bosons) with mass, while leaving the electromagnetic force's photons without mass.

This Higgs field may have played a role at the very beginnings of the universe: Physicists believe that at the highest energies, the electromagnetic and weak nuclear forces were unified, but something led to "electroweak symmetry breaking" as the infant cosmos cooled. That would be why the electromagnetic force and the weak nuclear force are distinct in the current universe. The Large Hadron Collider could shed new light on this mysterious Higgs mechanism.

Why so complicated?

Tim Jones / McDonald Observatory / HETDEX

Hadrons and leptons? Baryons and mesons? Fermions and bosons? Sometimes it seems as if particle physicists set up these classifications just to keep outsiders totally confused. But for researchers, these occasionally overlapping categories are useful for figuring out how different types of particles interact with each other.

In a sense, it's as if we've been talking about the game of chess but have gotten only to the point of naming the different pieces on the board: black pieces and white ones, pawns and knights, bishops and rooks, kings and queens. The real meaning of the game comes out when you start studying how the pieces perform and interact.

Heart of the machine

A worker stands inside the ATLAS detector, surrounded by its eight toroidal magnets, just before the installation of the machine's calorimeter. ATLAS, the largest particle detector at Europe's Large Hadron Collider, sits inside an underground cavern as big as a cathedral.
(Maximilien Brice / CERN)
ShareBack to slideshow navigation

Mission control

Members of the ATLAS detector team monitor operations at their control room on the campus of Europe's CERN particle-physics research center. A cutaway view of the particle detector can be seen on the computer screen at far right.
(Claudia Marcelloni / CERN)
ShareBack to slideshow navigation

Down the hole

The last of 1,746 superconducting magnets is lowered into the Large Hadron Collider's beamline tunnel via a specially constructed pit in April 2007, as seen in this fish-eye view. Dipole magnets like this one produce a magnetic field that is 100,000 times stronger than Earth's, to bend beams of subatomic particles around the circular accelerator.
(Claudia Marcelloni / CERN)
ShareBack to slideshow navigation

Wheel of fortune

One of the wheel-shaped slices of the ATLAS muon detector is lowered into a cavern for assembly into a giant device designed to look for evidence of exotic subatomic particles such as the Higgs boson. The Higgs particle is thought to play a key role in producing the property of mass in the universe.
(Claudia Marcelloni & J. Pequenao / CERN)
ShareBack to slideshow navigation

The theorist and the experiment

World-famous theoretical physicist Stephen Hawking takes a look at the Large Hadron Collider's underground beamline during a visit in September 2006.
(CERN)
ShareBack to slideshow navigation

Pulling the trigger

Each experiment at the Large Hadron Collider requires a "trigger," a combination of hardware and software that decides which collisions are significant enough to pass along for further analysis. This is a fish-eye view inside the trigger chambers for the ALICE detector's muon spectrometer.
(Aurelien Muller / CERN)
ShareBack to slideshow navigation

Inside the big bang

A technician from the ALICE installation team works on gas pipes for the detector. ALICE is designed to study lead-ion collisions so intense that they re-create the conditions that existed just after the big bang.
(A. Saba & Mona Schweizer / CERN)
ShareBack to slideshow navigation

Cycles within cycles

Dwarfed by science

The LHCb detector is designed to study why matter dominates over antimatter in the universe. The worker peeking out from the concrete barriers at left is dwarfed by the detector's lip-shaped magnet assembly at right.
(CERN)
ShareBack to slideshow navigation

The PC farm

CERN's Computer Center stores the quadrillions of bytes of data generated by experiments at the Large Hadron Collider and distribute the information to thousands of researchers around the world, using a network known as the LHC Computing Grid.
(Maximilien Brice / CERN)
ShareBack to slideshow navigation

Editor's note:
This image contains graphic content that some viewers may find disturbing.